September IPM Insect Scouting Tips
Soybeans
Continue scouting for corn earworm, stink bugs, and soybean looper in double-crop fields. Defoliation thresholds at R5 are 15% and between 20 and 30% at R6. Corn earworm pheromone trapping information for Maryland can be found at https://extension.umd.edu/resource/corn-earworm-pheromone-trapping. NC State Extension has a good CEW threshold calculator can be used to help decide if it is worth treating: https://www.ces.ncsu.edu/wp-content/uploads/2017/08/CEW-calculator-v0.006.html. Stink bug thresholds are 5 bugs per 15 sweeps until the soybeans reach the R7 stage, after which treatment for stink bugs is not necessary.
As the month progresses and fields get closer to harvest, sample stems in any field with a history of Dectes stem borer issues. If the field has a large stem infestation, prioritize that field for as timely a harvest as possible to reduce loss due to lodging.
Sorghum
Sugarcane aphids have been found on the Eastern Shore. This week's cooler weather should slow down their reproduction rate, but if we get some warm days in September, that might change. To scout, check the 50 plants in 4 different locations at least 25 feet into the field. If honeydew is present, check the upper and lower canopy of 15-20 plants for aphids. Treatment thresholds are when the field has an average of 50 and 125 aphids per leaf or 30% infested plants with localized areas with honeydew present. David Owen from UDel recommends using Sefina, Sivanto, and Transform for control. See Texas A&M “Scouting Sugarcane Aphids” handout for more information.
This article appears on September 2021, Volume 12, Issue 6 of the Agronomy news.